In the meantime I’ve heard lots of combinations. I was told to calculate TAS and take into account the wind, so this ultimately results in GS. The reason was, that by this the flightlog one obtains automatically from the software (e.g. FF) should match the actual times flown. Because of course during training one still logs all overflight times for the case of comm failures.
This sounded quite reasonable to me. On a 6 hours flight with a 30 knots wind the times obtained can differ quite significantly. But if you indicate the expected time of arrival without wind then it’s way out.
Indicating TAS sounds, to the other side, reasonable, because the controller needs to know how fast one moves in relation to other aircraft, for separation purposes. And the only reliable information for this is TAS.
So should one indicate TAS as speed, but calculate the times (most importantly ETA) including the expected wind?
How do you do this?
SkyDemon gives me the enroute time fed by the data previously entered in each airplane’s profile, and the present conditions, easy.
I usually add a “loiter” factor since I’m no AP addict 🤓
Yes, it’s TAS in the plan.
GS and ETA would be calculated by the software using the wind forecast
If your speed or level changes enroute, it can be adjusted per point by writing POINT/N0200F090 for each change. It’s A for altitudes instead of F.
The description of the flight plan form in PANS-ATM (ICAO doc 4444) is explicit in that it should be the true air speed. ICAO Annex 2 and SERA refers to the speed as “cruising speed” which can also only be interpreted as TAS.
There are lots of angles on this; firstly according to whether VFR or IFR.
VFR FPs are almost never checked for validity, and when they are nobody is likely to look at the TAS or EET unless obviously outrageous.
IFR FPs are always sent to Eurocontrol where the software checks them against their “secret performance model”. My tests (posted previously) suggests that – for a TB20 at least) they allow an EET margin (and thus a TAS margin) of 1.6 times around their secret model figure, which is quite a lot. The Autorouter has implemented a heavily “purist” approach where the EET is calculated and cannot be changed so where you need to do this to e.g. hit a purchased airport slot you have to use a service like eurofpl.eu which allows values to be entered directly. Use the AR to generate the route and paste it into eurofpl.eu.
Yes it is TAS but as I say nobody is going to notice if you use IAS or even GS 
Peter wrote:
The Autorouter has implemented a heavily “purist” approach where the EET is calculated and cannot be changed so where you need to do this to e.g. hit a purchased airport slot you have to use a service like eurofpl.eu which allows values to be entered directly. Use the AR to generate the route and paste it into eurofpl.eu.
AFAIK you could edit your Autorouter aircraft model (speed @ FL with Fuel Flow) and will be used later for all new flight plans.
If you enjoy pain, yes 
But anyway editing the AR perf model (which I originally created for the TB20, when I was a beta tester / admin on the AR) to hit a desired EET is way too much work especially if you are trying to get into EDNY by a hack and AR puts in the wind forecast which screws up your EET. In reality nobody is going to be doing this.
Back on the topic, I also don’t think the specified TAS is checked against the FP distance and the filed EET. Eurocontrol applies generous margins to all these. I just use 150kt on all FPs filed manually, and let the AR drop in whatever figure it feels like doing; it seems to like 140kt…
Udo mentions FF so he was probably talking about IFR FPs. I did play with FF for IFR FP filing a while ago… it also has a perf model but I never actually did any flights with it for real as there were too many UI problems.
